Turkish Journal of Fisheries and Aquatic Sciences 15: 851-859 (2015)

www.trjfas.org ISSN 1303-2712

DOI: 10.4194/1303-2712-v15_4_08

© Published by Central Fisheries Research Institute (CFRI) Trabzon, Turkey in cooperation with Japan International Cooperation Agency (JICA), Japan

Selectivity and Catch Efficiency of Three Spinner Hook Sizes in Angling for

Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792) in Karakaya Dam

Lake (Eastern Turkey)

Introduction

Recreational fishing, a leisure activity enjoyed

by many people throughout the world (Hickley and

Tompkins, 1998; Ditton, 2008; Arlinghaus and

Cooke, 2009), has an economic value estimated in the

hundreds of millions, or perhaps billions of dollars

annually in the United States and in the European

Union, among other regions (Ditton, 2008).

Fisheries managers are frequently tasked with

developing and maintaining quality recreational

fishing opportunities while protecting a population’s

aquatic resources. The use of recreational fishing

regulations as a management tool can have a

substantial effect on fisheries and, if used

appropriately, can enhance angling opportunities

(Bloom, 2013). Recreational fishing is a small-scale

fishing activity which is performed in inland or

marine waters (Hickley and Tompkins, 1998). Fishing

gear and duration of the operations significantly affect

the catch composition (Kaykaç et al., 2003), the catch

per unit effort (CPUE) and the yield per unit effort

(YPUE) efficiency. In addition to these parameters,

other important issues (e.g. hook size, environmental

changes) must be considered in recreational fishery.

The fundamental property of the indirect method

Tuncay Ateşşahin1,*, Erdal Duman1, Mehmet Cilbiz2 1 Firat University, Fisheries Faculty, Elazığ, Turkey. 2 Eğirdir Fisheries Research Institute, Eğirdir, Isparta, Turkey.

* Corresponding Author: Tel.: +90.424 237 0000; Fax: +90.424 2122780; E-mail: tatessahin@firat.edu.tr

Received 20 May 2015 Accepted 20 December 2015

Abstract

The aim of this study was to determine the relationship between spinner hook sizes (2, 3 and 4) and hook selectivity for

Oncorhynchus mykiss (rainbow trout), a species important to recreational fisheries in Karakaya Dam Lake in Eastern Turkey.

A total of 24 sampling trips were carried out twice per month by the same three anglers from May 2013 to April 2014. The

SELECT method was used to determine the selectivity parameters. An analysis to determine the differences in the catch per

unit effort (CPUE), yield per unit effort (YPUE) and condition factor values based on different hook sizes was conducted

using one-way ANOVA. During the spinner hook-size experiments, we captured 202 Oncorhynchus mykiss, which ranged

from 14.5 cm to 46.0 cm TL in length and weight 30.2 g to 1320.2 g. The mean lengths (±SE) of Oncorhynchus mykiss

captured on the three spinner hook sizes were determined. The optimum lengths calculated by log-normal model were found

to be 18.28, 27.41 and 36.55 cm for No 2, No 3 and No 4 hook sizes, respectively.

Keywords: Hook selectivity, rainbow trout, Oncorhynchus mykiss, catch efficiency, Karakaya Dam Lake.

Karakaya Baraj Gölü Gökkuşağı Alabalığı'nın (Oncorhynchus mykiss Walbaum, 1792) Üç Farklı Spinner

İğne Seçiciliği ve Avcılık Etkinliği

Özet

Bu çalışmada, Karakaya Baraj Gölünde amatör balıkçılıkta önemli bir tür olan Oncorhynchus mykiss’in avcılığında

kullanılan farklı boyuttaki spinner kancaların (2, 3 ve 4) seçiciliği ve avcılık verimlikleri araştırılmıştır. Mayıs 2013 - Nisan

2014 tarihleri arasında aynı oltacılarla ayda iki kez ve toplamda 24 avcılık operasyonu gerçekleştirilmiştir. Seçicilik

parametrelerinin belirlenmesinde SELECT metot kullanılmıştır. Ayrıca kanca numaralarına göre CPUE, YPUE ve K değerleri

istatistiksel olarak değerlendirilmiştir. Yakalanan 202 Oncorhynchus mykiss 14,5-46,0 cm toplam uzunluğunda, ağırlıkları

30,2-1320,2 g arasında değişkenlik göstermiştir. 2, 3 ve 4 numaralı iğnelerin optimum yakalanma boyları sırası ile 18,28,

27,41, 36,55 cm olarak bulunmuştur.

Anahtar Kelimeler: İğne seçiciliği, gökkuşağı alabalığı, Oncorhynchus mykiss, avcılık verimi, Karakaya Baraj Gölü.

852 T. Ateşşahin et al. / Turk. J. Fish. Aquat. Sci. 15: 851-859 (2015)

is that a functional relationship is being fitted to catch

data with no information about the sampled

population. Therefore, a method that tests various

functions against catch data, such as the Share Each

Length’s class Catch Total (SELECT) method (Millar

1992), could prove useful. There are numerous ways

of measuring hook dimensions, including total length,

gape, throat, wire diameter, bite, barb, shank, front

length, offset and bend (Campbell et al., 2014). In this

study, we chose to measure total hook size, since, in

Turkey, spinner-hook models are sold according to

their total length.

Substantial interest and research have focused on

hooking mortality based on gear, hook type and fish

species; however, less effort has been put into

evaluating the probability of capture associated with

these variables (DuBois and Dubielzig, 2004; Meka,

2004; Bloom, 2013). It is critical that fishery

managers evaluate, adopt and monitor special

regulations with specific strategies and objectives.

This approach will allow for the assessment of

regulations and associated responses within a fishery

activity (Bloom, 2013). Minimum legal sizes are the

most common tools used worldwide to manage

recreational fisheries (Alós et al., 2009). While the

size-selective nature of gear, such as trawls (Wileman

et al., 1996; Tokaç et al., 2004) and gill nets (Kalaycı

and Yeşilçiçek, 2012), are well known, there is still

no clear consensus on the form of the size-selection

curve for hooks on longlines (Czerwinski et al., 2010;

Campbell et al., 2014). Especially in Turkey, there are

few studies on hook selectivity and efficiency with

respect to recreational fisheries. The aim of this study,

therefore, was to determine the hook selectivity and

catch efficiency associated with fishing for

Oncorhynchus mykiss in Karakaya Dam Lake in

Eastern Turkey.

Materials and Methods

Karakaya Dam Lake, located in Eastern Anatolia

(Turkey), is one of the region’s largest and most

important water sources, both for irrigation and for

fisheries. The lake’s surface area is 268 km2, and its

reservoir volume, at normal water-surface elevation,

is 9,580,000 hm3 (Ozmen et al., 2006) (Figure 1).

Figure 1. Study area and fishing station in Karakaya Dam Lake, Region 10.

T. Ateşşahin et al. / Turk. J. Fish. Aquat. Sci. 15: 851-859 (2015) 853

From May 2013 to April 2014, a total of 24

fishing trips were carried out twice per month by the

same three anglers at Karakaya Dam Lake, Region 10

(Figure 1). The depth of the fishing areas varied

between 2–15 m, based on samplings conducted by

three anglers using identical hook sizes (i.e. 2, 3 and

4). For the experimental angling sessions, three

anglers with similar levels of experience were

selected. The duration of each sampling was fixed and

limited to 4 hours. Experimental trials were carried

out at 08:00 and 12:00 a.m. A technical plan of the

fishing line of the spinner used is shown in Figure 2.

The spinner hook sizes were approximately No2 = 2

cm, No3 = 3 cm and No4 = 4 cm (Figure 1). The total

length (TL) of all individual samples was measured to

the nearest 0.1 cm using a 100 cm ruler, and weight

(W) was measured using a digital scale with a

precision of 0.1 g.

The CPUE and YPUE values, calculated with

the formula recommended by Godøy et al. (2003) and

customized by Aydın (2011), are presented below.

Condition factor (K) was calculated according to

Fulton (1911); the relevant equation is shown below.

W= Weight (g) L= Total length (mm)

To determine the differences in CPUE, YPUE

and K value by different hook sizes, a one-way

ANOVA test was used. To perform a statistical

analysis, R version 3.1.2 (R Development Core Team,

2013) software was used.

The SELECT method was used to determine the

selectivity of each hook type (Millar, 1992; Millar and

Holst, 1997; Millar and Fryer, 1999). This method

assumes that the number of fish of a particular length

lj (j = 1, 2, 3, ... n) caught with a hook size mi (i = 1,

2, 3, … k) has a Ylj Poisson distribution, defined by

the following equation:

[Ylj~P0(pj. λl)]

where λl is the abundance of fish size l caught on

the hook; pj (l) is the relative fishing intensity (the

relative abundance of fish size l that j hook size can

catch). The Poisson distribution of the number of fish

size l caught by fishing gear with J hook size is

defined as [Nlj~P0 (Pj.λl.rl(J))]and is the selectivity

curve for j hook size (Acarlı et al., 2013; Öztekin et

al., 2014).

The log-likelihood of is as follows:

The most suitable model was chosen as the one

with the lowest deviation. Model equations of the

SELECT method are as follows:

Normal Location:

2

2

2

.exp

jmkL

Normal Scale:

22

2

2

1

.2

.exp

j

j

mk

mkL

Figure 2. Technical plan of spinner used in experiment.

854 T. Ateşşahin et al. / Turk. J. Fish. Aquat. Sci. 15: 851-859 (2015)

Gamma:

jj mk

L

mk

L

.1exp

..1

1

Log-Normal:

2

2

12

1 2

loglog

2logexp

1

m

mL

m

m

L

j

j

Bi-modal:

22

4

2

3

22

2

2

1

.2

.exp.

.2

.exp

j

j

j

j

mk

mkLc

mk

mkL

The Kolmogorov-Smirnov (K-S) test was used

to determine differences between size frequency

distributions of fish caught by hooks of varying sizes

(Siegel and Castellan, 1989; Karakulak and Erk,

2008; Aydın, 2011).

Results

A total of 202 O. mykiss were caught via a

spinner fishing technique during the study. These fish

ranged in size from 145 to 460 mm TL and number

(50, 88 and 64), mean lengths 24.8 ± 0.6 cm, 27.7 ±

0.5 cm and 29.3 ± 0.6 cm for hook sizes 2, 3 and 4,

respectively. Numbers, sizes and weights of catches

for each hook size are presented in Table 1.

There were significant differences in the average

total length of retained fish according to different

hook sizes, especially hook No2, which caught fish

that were smaller than those caught by No3 and No4

(Figure 3).

The CPUE value increased in proportion to

increases in hook size. There were statistically

significant differences between different hook sizes

and the CPUE values (P<0.05). It is thought that, in

this case, the samples would yield more large fish

than small fish in this location. Similarly, the YPUE

value also increased in proportion to increases in the

hook length. We detected significant differences on

the hook sizes with the No2 hook versus the No3 and

No4 hooks by an ANOVA test (P<0.05). However,

there were no statistical differences in the fish-

condition factor based on different hook sizes (Table

2) (P>0.05).

Although the number of fish caught did not

change based on the hook size (P>0.05), the No3

Table 1. Descriptive statistics of catch by different hook sizes

Hook

Number

Total length (cm) Total Weight (g)

N Mean Min. Max. Mean Min. Max.

2 50 24.8 (0.6) 14.5 32.4 196.4 (13.5) 30.2 411.3

3 88 27.7 (0.5) 17.4 46.0 278.5 (20.6) 63.4 1320.2

4 64 29.3 (0.6) 19.5 40.9 328.1 (24.7) 60.4 1020.4

Standard errors are in parentheses.

Figure 3. Average total length and the error bars plot by different hook sizes.

T. Ateşşahin et al. / Turk. J. Fish. Aquat. Sci. 15: 851-859 (2015) 855

hook was found to be more effective in terms of

catching efficiency (Table 1). On the other hand, hook

size had a significant effect on the length of the fish

caught (P<0.05), according to variance analyses

results that examined different hook sizes in relation

to the CPUE value. The length of fish caught

increased along with an increase in hook size (Table

2).

The selectivity parameters for equal catch efforts

were estimated with five models (Table 3). A log-

normal model was accepted as a compatible model

because its deviance is the lowest. Selectivity curves

and deviance residuals of the model are shown in

Figure 5 and in Figure 6, respectively.

The optimum length and spread values

calculated by the log-normal model (shown in Table

4) were found to be 18.28, 27.41 and 36.55 cm for

No2, No3 and No4 hook sizes, respectively.

According to the K-S test result (Table 5), there

were significant differences in the length frequency

distributions of fish captured with hook size No2

when compared with those of No3 and No4, but

significant differences were not observed in the length

frequency distributions of fish captured with hook

sizes No3 and No4 (Figure 4). This finding is

consistent with the ANOVA test results.

Table 2. Comparison of CPUE, YPUE and K value by different hook sizes via one-way ANOVA test

Parameter Hook No Mean+SE df MS F p

CPUE

2 0.174 (0.03)a 2 0.054 3.292 0.05

3 0.224 (0.03)b

4 0.307 (0.05)ab

YPUE

2 34.08 (6.80)a 2 8516.07 5.435 0.009

3 85.09 (14.18)b

4 72.91 (12.02)b

K

2 1.167 (0.03) 2 0.002 0.059 0.943

3 1.169 (0.02)

4 1.178(0.02)

Standard errors are in parentheses

Table 3. Results of the models fit using the SELECT method for hook sizes selectivity estimation

Model Parameters

Equal fishing power

Estimates Mode 1 Spread 1 Mode 2 Spread 2 Deviance df

Normal location k

σ

8.80(0.28)

8.64(0.82)

17.60(0.56) 8.66(0.82) - - 17.78377 28

Normal scale k1

k2

9.88(0.33)

0.56(0.04)

19.768(0.67) 6.58(0.69) - - 18.33871 28

Lognormal μ1

σ

3.01(0.03)

0.33(0.03)

18.28(0.60) 7.35(0.94) - - 15.03620 28

Gamma k

α

1.04(0.19)

9.96(1.77)

18.79(0.62) 6.61(0.68) - - 15.60996 28

Bi-normal k1

k2

k3

k4

c

3.016

0.332

5.154

0.292

1.551

18.29(0.16)

7.36(0.19) 159.06(-) 80.82(-) 15.03970 25

Model Parameters

Fishing power α hook size

Estimates Mode 1 Spread 1 Mode 2 Spread 2 Deviance df

Normal location k

σ

9.79(0.34)

9.44(1.04)

19.59(0.69) 9.44(1.04) - - 17.66359 28

Normal scale k1

k2

10.91(0.31)

9.69(1.83)

21.83(0.62) 6.22(0.58) - - 18.86084 28

Lognormal μ1

σ

3.12(0.03)

0.33(0.00)

20.41(0.71) 8.21(1.21) - - 15.03597 28

Gamma k

α

1.04(0.19)

10.96(1.77)

20.89(0.67) 6.94(0.76) - - 15.60996 28

Bi-normal k1

k2

k3

k4

c

3.12

0.33

4.28

0.09

2.40

20.41(0.71) 8.21(1.22) 71.94(-) 7.20(-) 15.03599 25

Standard errors are in parentheses.

856 T. Ateşşahin et al. / Turk. J. Fish. Aquat. Sci. 15: 851-859 (2015)

Discussion

The selectivity of fishing gear is an important

fishery management tool in terms of giving at least

once changes of reproduction to fish. In many parts of

the world many studies have been done on the

selectivity of various fishing gear, but there has been

no research on the selectivity of spinner hook size,

Figure 4. Length- Frequency of O. mykiss by different hook sizes.

Figure 5. Selectivity curves of hook sizes for the O. mykiss.

Figure 6. Deviance residuals of hook sizes for the O. mykiss.

T. Ateşşahin et al. / Turk. J. Fish. Aquat. Sci. 15: 851-859 (2015) 857

although spinner hooks are the most important fishing

gear used in recreational fishing. When amateur

fishermen, who’s number more than commercial

fishermen, are taken into account, the importance of

this study is evident.

Estimates of size selectivity of fishing gear

provide important information regarding the

conservation of fishery resources (Czerwinski et al.,

2010). Moreover, fishing-gear selectivity is one of the

most important pieces of information needed to

manage a fishery and is used to detect the minimum

catchable length for the purpose of determining the

target species and, subsequently, the gill-net mesh

size (Sparre et al., 1989) and in determining the hook

size (Czerwinski et al., 2010; Öztekin et al., 2014).

Researchers have conducted much research on

the topic of amateur fishing, especially with respect to

the O. mykiss species. These researches generally

focused on the effects of fishing hooks on fishing

efficiency, catch and release (Meka, 2004), hook

injury and hook damage (DuBois and Dubielzig

2004); however, studies on the selectivity of hook size

are limited. In this study, the selections of the spinner

hook sizes used were made according to the SELECT

method. It is necessary to take into account selectivity

studies in terms of fishery management. The size of

the spinner hook is recommended to be smaller than

No3.

The results obtained in this study revealed that

hook size affected the size of the captured fish,

consistent with other selectivity studies. This study

also showed that hook size compliancy was different

for each population: the number of captured fish in

this study was 50 with an No2 hook, 64 with an No4

hook and 88 with an No3 hook. This result shows us

that the size distribution in a population has an

important effect on the catchability of fish based on

different hook sizes. Consequently, more studies

should be done on the selectivity of different fishing

gear in the context of fishery management in Turkey.

Öztekin et al. (2014), in a study of Phycis

blennoides in Saros Bay, conducted research on the

selectivity of bottom longlines using the SELECT

method and found that 6, 7, 8 and 9 hook sizes were

optimal for capturing fish with lengths of 48.45,

41.49, 37.44 and 32.35 cm, respectively.

Amarasinghe et al. (2011) studied Caranx ignobilis

and Carangoides gymnostethusin terms of hook

selectivity [a modification of Baranov-Holt’s method

for gill-net selection (Baranov, 1914; Holt, 1963) was

employed, as explained by Pauly (1984)]; Lop size for

C. ignobilis 8, 9, 10 and 11 mm hook sizes,

respectively, for capturing fish with lengths of 16.7,

22.4, 27.1 and 33.9 cm; C. gymnostethus for 10, 11,

12 and 13 mm hook sizes, respectively, for capturing

fish with lengths of 29.9, 39.1, 45.9 and 56.9 cm. The

authors found a relationship between optimum size of

capture and hook size. In this study, we found that the

optimal hook sizes for capturing fish with lengths of

18.28, 27.41 and 36.55 cm, are No2, No3 and No4,

respectively. These results are consistent with those of

Oztekin et al. (2014) and Amarasinghe et al. (2011).

Our study showed that the selectivity curve has quite

a wide size range (Figure 5), a finding that is similar

to that reported by Campbell et al. (2014) regarding

Rhomboplites aurorubens, Lutjanus campechanus and

hook types and which conforms to the selectivity

curves.

The O. mykiss is not a species native to

Karakaya Dam Lake and was introduced after the

activities of the trout aquaculture in a net cage. The

fish have an important place in the day-to-day fish

populations of dam lakes; thus, it is very important, in

terms of economic value, for fish to be brought into

recreational fisheries (Ateşşahin et al., 2011). Cilbiz

et al. (2015) reported that gill-nets are not efficient for

O. mykiss fishing and recommended that angling

should be encouraged for this species in dam lakes.

There are no legal-length regulations (minimum

landing size) on O. mykiss fishing in Turkey, because,

according to the circular (Turkish Amateur Fishery

Regulations No: 2012/66), which regulates

recreational fisheries, fish classified in unfavourable

species categories have ecological aspects that must

Table 4. The optimum lengths and spread values of O. mykiss according to the lognormal (it has lowest deviance value)

Hook Number Model Length (cm) Spread Value (cm)

2 18.28 7.30

3 27.41 10.95

4 36.55 14.60

Table 5. Result of the K-S test used to compare length frequency distributions of catch

Hook 1 Hook 2

Kolmogorov-Smirnov Test

D max Critical Values (α=0.05) Decision

2 3 0,2600 0.2389 H0Reject

2 4 0.4071 0.2534 H0Reject

3 4 0.2119 0.2196 H0Not Reject

Ho: There are no significant difference between length frequency distributions (α=0.05, K=1.36).

858 T. Ateşşahin et al. / Turk. J. Fish. Aquat. Sci. 15: 851-859 (2015)

be considered. However, fishing for O. mykiss that are

of less than a portion-size weight (180–200 g) may be

a troublesome situation in terms of a bioeconomic

approach. The portion length of O. mykiss has been

reported as 27.04 cm (total length) in Karacaören I

Dam Lake by Cilbiz et al. (2015). In this context,

hooks less than No3 (3 cm) should not be used in O.

mykiss fishing in Karakaya Dam Lake.

Acknowledgements

We thank the followings for their help at field

work; Ergün ASLAN, M.M. ÖZMEN, Taner Şener,

A.Erkam ÇETİN.

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